Current methods, whether from instrumental sensitivity or design, have not been capable of effectively studying the structure and/or function of pulmonary surfactant proteins. It is crucial for the development of treatments for NRDS and ARDS that the mechanisms by which these proteins function be determined. This will be accomplished by combining a sensitive infrared spectroscopic technique (ATR-FTIR) with a unique captive bubble surfactometer (CBS) to yield a method that will be capable of defining lipid/protein interactions and surfactant protein structure of preparations that accurately mimic physiological conditions. The goals of the proposed research are to optimize parameters for FTIR spectral acquisition in the CBS/ATR-FTIR sample chamber, to optimize parameters and instrumentation for surface tension measurements by the CBS component, and to integrate all components of the CBS/ATR-FTIR sampling accessory for complete computerized instrumental control and data acquisition. This configuration will permit simultaneous measurement of 1) monolayer surface pressure, 2) protein structure (as a function of surface pressure), 3) protein and lipid orientation (vs. surface pressure), and 4) protein/lipid interactions of surfactant proteins and other proteins (e.g., membrane receptors, antimicrobial peptides) at a lipid monolayer interface. Simultaneous structure/function measurements by CBS/ATR-FTIR will make it possible to delineate the role of each surfactant protein in the biological function of pulmonary surfactant in healthy and diseased lungs. In the near future, experiments with more complex surfactant protein/lipid mixtures may aid in the improvement and development of treatments for surfactant deficient diseases in infants, children and adults.